Epitaxial Growth And The Study Of Physical Properties Of Nickel Telluride

The compounds composed of transition metal elements and chalcogenides will show some physical properties in some fields.Mo S₂ has a band gap that varies with the number of layers,and has a very broad application prospect in the fields of optoelectronics,catalysis and sensors.Nickel and tellurium are transition metal elements and sulfur elements,respectively,and their nickel-tellurium compounds will show different physical properties because of their different valence states.Ni Te₂material is a new type of Dirac semi-metallic material of the second kind,which has unique advantages in the field of studying plane Hall effect.Ni₅Te₆ material has superconductivity,which can provide an ideal platform for exploring new superconductivity,quantum criticality and strong electron correlation effects and preparing new superconducting devices.At present,the preparation of nickel telluride mostly adopts chemical solution synthesis and chemical vapor deposition,and the nickel telluride prepared by these two methods has many defects,which seriously affect its intrinsic electronic properties.In this paper,using molecular beam epitaxy（MBE）to directly telluride Ni（111）substrate,several high-quality nickel telluride alloy structures have been prepared under different coverage of Te atoms.We will focus on 2（3）^1/2×2（3）^1/2 phase and 3×3 phase,the main contents are as follows:（1）When the deposition amount of Te atoms is low,and the deposition time is 4minutes,there is a 2（3）^1/2×2（3）^1/2.The hexagonal honeycomb shaped ordered structure of nickel telluride with triple symmetric defect morphology.At 9 minutes of deposition,the coverage of 1/12 ML（monolayer）is achieved,and the triple symmetric defects disappear.At this time,the number of ordered structures increases but the area of individual islands decreases.The theoretical calculation results indicate that the energy band of the structure exhibits characteristics of metallic properties.（2）When the deposition amount of the Te source is high,and the deposition time is 9 minutes,the coverage of the Te atom is 1/9ML,and there appears a 3×3 hexagonal densely stacked nickel telluride structure.Through the analysis of STM experimental data,it can be found that the lattice constant of 3×3 hexagonal close-packed nickel telluride structure is 7.54（?）,which is basically consistent with 7.44（?）,the lattice constant measured by the simulated atomic structure model.At the same time,the energy band structure corresponding to this structure is calculated by the First Principle Method.The results show that there is no obvious band gap in the energy band structure and this structure shows metal properties.In addition,in order to explore the transformation process of 2（3）^1/2×2（3）^1/2 and 3×3 structures with the change of the coverage of Te atom.We have carried out several repeated experiments whose results vary with the change of the coverage.It is found that 2（3）^1/2×2（3）^1/2 structure will not be formed on the atomic-level clean impurity free substrate,but 2（3）^1/2×2（3）^1/2 structure can be grown only on the substrate with impurities.The experimental results show that 2（3）^1/2×2（3）^1/2 structure is induced by impurities.In this paper,the growth law of nickel telluride with the change of tellurium coverage is explored,the change of Te atom coverage deposited on Ni（111）substrate will promote the phase transition of nickel telluride.We studied the structure and phase transition process of two kinds of nickel telluride structures by scanning tunneling microscope,which laid a foundation for the future study of electronic properties and other physical properties of nickel telluride materials.